An act of terrorism against commercial shipping or the ports they use in Australia could have massive human and economic consequences. The Australian Government's approach to countering maritime terrorism has been incremental and slow to evolve but terrorists have demonstrated the capacity to adapt rapidly and outpace government policy. Counterterrorism policy in the maritime environment faces many challenges. Protecting vessels and maritime infrastructure against a potential attack is not only costly but difficult. The capacity of the Australian Government to act is limited by the need to comply with international maritime law and the requirement to negotiate with state governments where jurisdictions overlap. This paper will consider the difficulty of implementing counterterrorism policies against the threat from small vessels to Australian maritime infrastructure. It will also argue that the current maritime security regime can be substantially improved.